机载天线罩透波窗结构参数优化分析

在考虑机载气动载荷影响的情况下,运用ANSYS 软件对某机载天线罩透波窗开口形状和复合材料铺层顺序等结构参数变化分别进行力学仿真分析,依据仿真结果确定了该天线罩透波窗结构的优化参数,比较明显地降低了该天线罩透波窗结构在气动压力作用下的正应力和剪切应力水平。     

双旋弹道修正弹弹体非对称载荷的数值研究

固定鸭舵双旋弹道修正弹的弹体受到鸭舵非对称尾流的影响,其载荷具有非对称特性。为了研究该非对称特性,通过计算流体力学(CFD)仿真和风洞实验的结果对比验证CFD方法的有效性。对0°舵偏、2°舵偏、4°舵偏的双旋弹道修正弹模型在多马赫数、多攻角下进行CFD仿真,并通过绘制鸭舵尾流的流线图和弹体压力系数云图对流场进行定性分析,通过对比弹体截面压力系数和弹体法向力、侧向力系数对弹体受力的非对称性进行定量分析。结果表明： 0°舵偏模型的弹体压力系数呈面对称,2°舵偏模型、4°舵偏模型弹体压力系数呈非对称;在给定马赫数下,3种模型弹体法向力系数随攻角变化的曲线高度重合; 0°舵偏模型的弹体侧向力系数在0附近,2°舵偏模型、4°舵偏 模型的弹体侧向力随攻角近似线性变化,随马赫数先增大、后减小;给定攻角时,4°舵偏模型对应曲线峰值约为2°舵偏模型的2倍。     

An aerodynamic and aeroelastic experimental study on a sectional and three‐dimensional rectangular tall building

This paper examines the aerodynamic properties of a rectangular tall building with sharp edges. The building has a section aspect ratio B/D = 2.6 and a height aspect ratio H/D = 9, giving in a quite slender prismatic configuration. The study was performed on sectional and three‐dimensional models of the building. The sectional model was tested in a smooth flow condition, and the aerodynamic coefficients of the section were determined. Forces and pressure distributions were measured on the three‐dimensional model to compare with the aerodynamic behavior of the sectional model. Both a rigid (non‐moving) and a moving model of the building were tested to analyze possible aeroelastic effects. Different levels of incoming wind turbulence were tested, since this is a key parameter in the aerodynamic behavior of the rectangular prism. Copyright © 2015 John Wiley & Sons, Ltd.     

Aerodynamic impact of train-induced wind on a moving motor-van

The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles. This research introduced a validated computational fluid dynamics (CFD) model regarding this concern. Such an aerodynamic impact mechanism was explored; a relationship between the transverse distance between train and motor-van (hereinfafter referred to as van) and the aerodynamic effects on the van was explored to help the optimization of bridge decks, and the relationship between the automobile speed and aerodynamic variations of a van was fitted to help traffic control. The fitting results are accurate enough for further research. It is noted that the relative speed of the two automobiles is not the only factor that influences the aerodynamic variations of the van, even at a confirmed relative velocity, the aerodynamic variations of the van vary a lot as the velocity proportion changes, and the most unfavorable case shows an increase of over 40% on the aerodynamic variations compared to the standard case. The decay of the aerodynamic effects shows that not all the velocity terms would enhance the aerodynamic variations; the coupled velocity term constrains the variation amplitude of moments and decreases the total amplitude by 20%–40%.     

微气泡致动器技术在弹丸飞行中的应用

为研究不同的气泡高度对弹丸的影响,建立带有不同高度微气泡致动器弹丸的模型,对不同弹丸进行气 动仿真,分析带有不同高度的微气泡致动器对弹丸阻力系数所产生的影响,并计算出全弹道的飞行过程。仿真结果 表明：加装不同高度的微气泡对弹丸的飞行稳定性影响很小;相同马赫数、相同攻角情况下带有气泡致动器的弹丸 阻力系数小于普通弹丸,升力系数大于普通弹丸,能够有效地增大射程和减小横向偏移。     

On-line control of surface quality for an axially moving steel strip partially immersed in fluid under tension

An on-line control method of surface quality for continuous hot-dip galvanized steel strip after cooling is presented,which combines analytical dynamics theory of a thin plate with the finite element method. The inherent characteristics of the non-immersed and partially immersed strip in liquid zinc were calculated on the basis of theoretical analysis and numerical simulation,respectively. Multi-parameter fitting of the deviation between results using different methods was performed. To optimize the strip excitation frequency away from the resonance region,on-line vibration control of the strip near the air knife under full product conditions was achieved by changing the field production parameters based on the field test results. The results indicate that although the axial velocity has little effect on the inherent characteristics of the strip compared with other manufacturing parameters such as the steel specifications and tension,it induces external excitations,including moving the aerodynamic load and bearing vibration. To some degree,the vibration near the air knife can be reduced by strengthening the support stiffness of the contact rolls. A total on-line control program of surface quality for continuous hot-dip galvanized pure Zn and galvannealed steel sheet in the cooling section is proposed.     

Control of the aerodynamic characteristics of wing airfoils by nonstationary energy supply in transonic flow

The possibility of controlling the aerodynamic characteristics of wing airfoils in transonic regimes of flight using one-sided pulse-periodic energy supply has been studied. The flow structure near the symmetric airfoil at different angles of attack and its aerodynamic characteristics as functions of the value of energy in its nonsymmetric (about the airfoil) supply have been determined by numerical solution of two-dimensional nonstationary gasdynamic equations. A comparison of the obtained results and the data of calculation of flow past the airfoil at different angles of attack without energy supply has been made. It has been established that a prescribed lift can be obtained, using energy supply, with a much higher fineness ratio of the airfoil than that in the case of flow past it at an angle of attack. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 18–22, January–February, 2009.     

轴流式通风机气动声场的数值研究

介绍通风机气动噪声预测现状。将SIMPLE算法与Realizablek-ε湍流模型相结合,通过求解Navvier-Stokes方程,对两级轴流式通风机的三维定常流动进行数值模拟。通过引入基于Lighthill声学类比理论的宽频声源模型,对通风机内部气动噪声分布特性进行数值模拟,预测声功率分布情况,并提出相应的降噪措施,对通风机结构的优化设计及噪声控制具有重要的参考意义。     

Ash formation during pulverized coal combustion : 1: Aerodynamic influences

The elemental composition of pulverized fuel boiler deposits often differs markedly from that of the corresponding fly ash and coal ash. Evidence is given here to support the hypothesis that such chemical segregation could be induced by competition between aerodynamic drag and inertial forces on a particle in a curved streamline; this increases the probability of impacting the boiler walls for large particles of high density, leading to preferential deposition. A conventional air classifier was used to separate mono-sized samples of pulverized coal and char particles into aerodynamically different fractions, and to prepare vitrinite-char and inertinite-char concentrates. The relevance of such aerodynamic segregation is considered by comparing the enrichment (or depletion) of non-volatile elements in boiler ashes with that in ashes derived from air-classified char fractions. Common trends, particularly for iron (the major fluxing element) have been identified (i) between the highest density fractions and furnace deposits, and (ii) between the lower density fractions and cyclone ash.     

Experimental study of across‐wind aerodynamic damping of super high‐rise buildings with aerodynamically modified square cross‐sections

Across‐wind aerodynamic damping ratios are determined from the wind‐induced acceleration responses of 10 aeroelastic models of square super high‐rise buildings in an urban flow condition (exposure category C in the Chinese code) using the random decrement technique. Moreover, the influences of amplitude‐dependent structural damping ratio on the estimation of aerodynamic damping ratio are discussed. The validity of estimated damping is examined through a comparison with previous research achievements. On the basis of the estimated results, the characteristics of the across‐wind aerodynamic damping ratios of modified square high‐rise buildings are studied. The effects of aerodynamically modified cross‐sections, such as chamfered, slotted and tapered cross‐section, on the across‐wind aerodynamic damping ratio are investigated. The results indicate that modifications of cross‐sections are not always effective in suppressing the aeroelastic effects of super high‐rise buildings. Low corner‐cut ratios (chamfer ratios from 5% to 20% and slot ratios from 5% to 10%) and low taper ratio (1%) significantly decrease the magnitudes of absolute aerodynamic damping ratios. However, large modifications of cross‐sections (slot ratio of 20% and taper ratios from 3% to 5%) increase wind‐induced responses by changing the aerodynamic damping ratios. According to the database, empirical aerodynamic damping function parameters are fitted for high‐rise buildings with aerodynamically modified square cross‐sections. Copyright © 2013 John Wiley & Sons, Ltd.